Selena Gomez headed over to the Ed Sullivan Theater yesterday for a guest appearance on the Late Show With David Letterman. The 18-year-old singer was promoting her new single "Who Says" from her upcoming third album, looking like a rock star in an elaborate Emilo Pucci minidress and zipper-detailed rossette pumps. With its graphic-print skirt, embellished leather bodice, and laced long-sleeved top, it's a party dress if we ever saw one, but Gomez has good reason to celebrate: yesterday she confirmed her relationship with Justin Bieber. She says of his enraged and disappointed fans: "It hurts, it really does. I don't feel like I'm doing anything wrong. I've been best friends with him for a very long time. But I try not to focus on it. I have a strong family and great fans."